With pressure for miniaturization of end-user consumer products, there is continuing pressure to reduce the size of semiconductor packages that are used in such products, while at the same time providing greater functionality with the smaller semiconductor packages. This has resulted in a variety of surface mount semiconductor packages having smaller package outlines and a greater number of inputs and outputs.
One such package is known as the bumped chip carrier (BCC) package. A BCC package contains a semiconductor die that is connected via interconnecting wires to a plurality of terminals. The semiconductor die and the interconnecting wires are encapsulated in mould compound with the terminals exposed and secured onto the surface of the package.
The BCC package is formed by first forming a patterned layer of resist on an upper surface of a sheet of copper alloy. The patterned layer of resist has openings, and a half-etching process is used to etch cavities in the copper alloy at the openings. Then, layers of plating are formed on the inside surface of the cavities and the layer of resist is removed, forming a copper alloy substrate.
A semiconductor die is centrally mounted on the copper alloy substrate, and gold bumps are bonded to the layers of plating. Interconnecting wires are connected between the semiconductor die and the gold bumps. The semiconductor die, the interconnecting wires, the gold bumps, and the cavities are then encapsulated using a mould compound. The copper alloy substrate is dissolved away, leaving the plating layers, resembling small bumps, exposed to form the terminals. Such a structure is disclosed in European Patent Application EP 0773584A2, as entitled “Device Having Resin Package and Method of Produce the Same”.
There are several disadvantages associated with the BCC package including the difficulty of controlling the etching process to form the cavities on the copper substrate, and the final process of dissolving the copper alloy substrate. Such processes can adversely affect the integrity of the plating layer and also adversely affect mould locking between the semiconductor die and the mould compound. Another disadvantage is the need and cost of gold bumping which requires a specialized and dedicated machine. In addition, the relatively high cost of using and forming the copper alloy substrate, and later removing the copper alloy substrate altogether is another disadvantage.